[Pw_forum] Total energy diverges in cell relaxation

[Hui Tang]

Dear all,

I'm trying to do cell relaxation on my Mg-Boron systems. For some of the
structures, I got extremely strange results. The total energy diverges
starting from some ionic step. For example, here are the total energy in
each ionic step for one of the problematic run:

!    total energy              =   -24.47168660 Ry
!    total energy              =   -35.02062718 Ry
!    total energy              =   -38.37822321 Ry
!    total energy              =   -40.20237747 Ry
!    total energy              =   -40.96387007 Ry
!    total energy              =   -41.20956341 Ry
!    total energy              =   -41.41389316 Ry
!    total energy              =   -41.46640700 Ry
!    total energy              =   -41.49930067 Ry
!    total energy              =   -41.51263104 Ry
!    total energy              =   -41.53987139 Ry
!    total energy              =   -41.59139496 Ry
!    total energy              =   -41.55162726 Ry
!    total energy              =   -41.64537650 Ry
!    total energy              =   -41.67440874 Ry
!    total energy              =   -41.73712135 Ry
!    total energy              =   -51.60413428 Ry
!    total energy              =  -688.94041793 Ry
!    total energy              =  -817.40812316 Ry
!    total energy              =  -914.65691139 Ry
!    total energy              =  -980.98769592 Ry
!    total energy              = -1145.13424734 Ry
!    total energy              = -1079.87331043 Ry
!    total energy              = -1148.61890203 Ry
!    total energy              = -1147.67898328 Ry
!    total energy              = -1147.50188067 Ry
!    total energy              = -1148.72218340 Ry
!    total energy              = -1149.83861471 Ry
!    total energy              = -1690.39538237 Ry
!    total energy              = -2822.35642442 Ry
!    total energy              = -2718.63827111 Ry
!    total energy              = -2790.48198795 Ry
!    total energy              = -2823.74590405 Ry
!    total energy              = -2878.31317290 Ry
!    total energy              = -4478.65409327 Ry
!    total energy              = -5464.15854938 Ry
!    total energy              =-14818.93675687 Ry
!    total energy              =-17158.30103958 Ry
!    total energy              =-18287.28161766 Ry

and the forces:

     Total force =    39.327209     Total SCF correction =     0.000071
     Total force =    11.517813     Total SCF correction =     0.000029
     Total force =     8.564152     Total SCF correction =     0.000058
     Total force =     3.973671     Total SCF correction =     0.000035
     Total force =     1.056249     Total SCF correction =     0.000106
     Total force =     0.617165     Total SCF correction =     0.000092
     Total force =     0.326250     Total SCF correction =     0.000046
     Total force =     0.416678     Total SCF correction =     0.000033
     Total force =     0.227223     Total SCF correction =     0.000033
     Total force =     0.501912     Total SCF correction =     0.000042
     Total force =     0.269395     Total SCF correction =     0.000104
     Total force =     0.369080     Total SCF correction =     0.000049
     Total force =     0.334142     Total SCF correction =     0.000026
     Total force =     0.148318     Total SCF correction =     0.000034
     Total force =     0.145030     Total SCF correction =     0.000012
     Total force =     0.143331     Total SCF correction =     0.000064
     Total force =   116.856723     Total SCF correction =     0.000084
     Total force =    65.417648     Total SCF correction =     0.000066
     Total force =   171.381517     Total SCF correction =     0.000070
     Total force =   155.577114     Total SCF correction =     0.000070
     Total force =   184.877111     Total SCF correction =     0.000057
     Total force =   109.156982     Total SCF correction =     0.000037
     Total force =   142.602012     Total SCF correction =     0.000080
     Total force =    88.522593     Total SCF correction =     0.000117
     Total force =   127.562744     Total SCF correction =     0.000058
     Total force =    92.956163     Total SCF correction =     0.000108
     Total force =    88.462372     Total SCF correction =     0.000117
     Total force =    84.376621     Total SCF correction =     0.000056
     Total force =   134.526750     Total SCF correction =     0.000106
     Total force =   282.688334     Total SCF correction =     0.000132
     Total force =   600.035535     Total SCF correction =     0.000078
     Total force =   224.477965     Total SCF correction =     0.000122
     Total force =   398.869729     Total SCF correction =     0.000123
     Total force =   396.502768     Total SCF correction =     0.000149
     Total force =   420.885999     Total SCF correction =     0.000136
     Total force =   443.182054     Total SCF correction =     0.000031
     Total force =  3819.452849     Total SCF correction =     0.000261
     Total force =  1265.093632     Total SCF correction =     0.000207
     Total force =  1027.278240     Total SCF correction =     0.000338

For this problematic system, this behavior is very stable. No matter I use
'cg' or 'david', change the mixing parameter from 0.9 to 0.1, I still get
similar problem.

I cannot find anything relevant in the archive. I wonder if anyone knows
what's going on here and can help me get rid of this annoying problem.

btw, the input, output files and pseudo-potentials can be found at:
http://volga.eng.yale.edu/hui/MgonBS.tar.gz




Thank you very much,
---------------------------------------------
Hui Tang
Graduate Student
Department of Applied Physics
Yale University
Email: hui.tang at yale.edu
Phone: 1-203-432-7763
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